Numerous patents exists in the field of footwear. A primary purpose of footwear, namely shoes, is to protect the foot from injury. The sole of the shoe protects the foot and further operates to provide traction and cushioning. The cushioning may be as simple as a rubber slab or as elaborate as an air cushion.
Prior art shoes that incorporate a spring base were mainly novelty products providing an unpredictable platform that reacts to the various forces provided in direct relation to the tension of the spring. Springs incorporated into the heel of a shoe enhance cushioning but typically remain novelty products if the springs are not controllable. Various mechanics have been attempted to increase the cushioning effect of the heel.
U.S. Pat. No. 5,282,325 discloses a sports shoe having a spring disposed in the sole of a shoe. The spring operates to bias the foot in a raised position wherein the spring provides cushioning of the shoe against shocks from the ground. The spring utilizes a torsion spring placed along a longitudinal axis disposed horizontal to the ground using a spring constant to resist flexing of the spring. Further, the torsion spring placed along a horizontal plane inhibits complete compression of the spring as the coils cannot be collapsed.
U.S. Pat. No. 5,224,278 discloses another shoe having a spring base enhanced by an air bag positioned along the midsole for biasing the heel against shock.
U.S. Pat. No. 5,212,878 discloses a shoe having a biasing means placed in the sole. In this disclosure springs placed into the shoe allow the user to select the characteristics of the sole cushioning.
U.S. Pat. No. 5,138,776 discloses a shoe having a highly elastic heel for use in reducing the shock during running and jogging. The elastic heel operates as a cantilevered spring with no means for adjustment.
The problem remains in that it is not possible for the manufacturer of a shoe to envision the physical aspects of the purchaser of the product nor their use of the product. For instance, an average adult male having a 10-D shoe size can range from a short heavy-set person who may only walk for exercise to a tall athletic person who jumps rope for exercise. The point being the use of the shoe cannot be predicted as each person may not even know what they will use the shoes for. A consumer may use a shoe for various activities none of which would be appropriate for a particular shock absorbing spring shoe.
Most spring shoes are designed to accommodate average endeavors. For instance, an athletic person who purchases a spring based shoe may on one day choose to play basketball, another day play racquetball, another day he may simply walk a long distance. Each of these activities require various types of support for optimum comfort. The problem with a spring based shoe which may be appropriate for walking may be dangerous for basketball where quick stops are necessary. Thus, an individual may need to purchase numerous pairs of shoes to accommodate a range of activities.
In spite of the prior art, a clear need remains for better solutions to the problems addressed by the prior art, namely, the ability to relieve shock loads encountered by wearers of the footwear yet provide optimum comfort for a specific activity. There remains a need for consumer adjustable shock absorbing shoes.